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Topic Title: Ham radio grounding,pme system
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Created On: 08 June 2018 01:31 PM
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 08 June 2018 01:31 PM
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MrPaul

Posts: 13
Joined: 08 June 2018

Hi all I was told to come to this site for help.I have a ham radio receiver and on the back there is a ground connection.I have a pme electrical system. The reason for asking I get mains noise on low bands.is it ok to put a ground rod outside and connect my radio to?many thanks
 08 June 2018 02:07 PM
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broadgage

Posts: 2853
Joined: 07 August 2007

No simple yes or no to this one I am afraid.

If the radio equipment is double insulated and does not need a mains earth connection, then it MIGHT be acceptable, but probably not.
If the equipment is metal cased, but double insulated, then connection of an external earth rod is potentially dangerous.
You could end up with radio connected to a local earth rod, and say a portable heater with metal case connected to mains PME earth.
There could be a dangerous voltage between heater and radio.
Likewise a dangerous voltage might be present between metal plumbing and the radio.

If the radio is off all insulated construction and requires an earth ONLY to improve reception, then it MIGHT be OK to use an external earth rod. Still not ideal though.

If the radio is earthed to the mains/PME earth and you propose to connect an external earth rod IN ADDITION, then that should be fine, it is no worse than a gas boiler connected to true earth via the water and gas pipes, and to the PME earth.
In that case the external earth rod should be protected by an insulated enclosure to prevent it being touched.

If you are proposing to connect an earthed appliance to a local earth rod INSTEAD of to the PME earth, then in general, no.
 08 June 2018 02:41 PM
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mapj1

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One side of your antenna will be grounded to the radio earth. If you have an external antenna, if you like it or not you will both be exporting the power supply earth which may or may not connect to mains earth, and you will also bring in the external ground potential inside the building.
If you have an external antenna that is not grounded by design, then please for reasons of ESD protection have an external electrode, even if this connects via a spark gap and resistor, or gas discharge device. Wires in the sky can pick up very nasty voltages when there is a thunderstorm a few miles away. Note this is a functional earth for the radio and to bleed acquired charge off the antenna, not a safety earth for blowing the main fuse as part of safety/ ADS.
The ideal is to have a dedicated Radio Shack as a TT island, where the PME earth does not come near it, but indoors in part of a house where the rest is PME this is not normally practical.
Nor is it normally practical for a hobby installation to insist on a 10mm green and yellow wire from a converted dining table to the house main earth terminal.
As a more workable compromise, make the bench an appliance, rather than fixed wiring, take care not to mix and match radio earth and mains earth on the operating bench, and have a single point where all 3 cores of the mains to the bench can be isolated. ('in emergency unplug here')
Does the radio have a mains power supply internally, or is there an external transformer ? Most radios that take for example 12V (really 13.6) as an input expect neither side of the incoming DC to be mains earth, rather the negative side of the DC is connected to the radio (antenna) earth potential internally to the radio.

From an EMC perspective you may wish to put chokes in the mains earth, if there is a problem of mains borne interference, if so these must be sized with carrying enough current to blow the mains fuse in mind.

There are corner case solutions with isolation transformers either in the mains supply or in the RF path but this is not common.

edit addendum
The risk of a PME earth and a real terra-firma one being simultaneously accessible to the operator and far enough apart in voltage to be dangerous is real but modest - if it was not then street lights on PME wired estates would be surrounded by dead bodies. They are not normally. Estimates from a study looking at car charging in the UK are about once per thousand years for houses on any one substation.
That risk from PME must be balanced against the much larger risks from lighting or static induced shocks from a non-earthed antenna system.
And, as a radio op is an electrically skilled person (well some are) it may be possible to argue that they are less likely than the general population to keep using their equipment if the electricity is clearly playing up,and can be trusted to not bring mains earthed objects near the radio. One could even have a warning circuit between the 2 earths for example, to sound if the voltage is larger than some limit, but normally folk are just careful, and unplug the rig when not in use, and ground the antennas outside when a lightning state is expected.

73 de G7VZY

-------------------------
regards Mike


Edited: 08 June 2018 at 04:23 PM by mapj1
 08 June 2018 03:23 PM
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John Peckham

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Mr Paul

My transceiver is isolated from the mains earth as it is supplied from a 13.8V 30A power supply and the aerial is a 1/2 wave loft dipole.

The dipole has a 1:1 balun at the centre which cuts down on the noise.

I get loads of noise generated by my appliances with the computer kicking out bucket loads along with all my neighbors.

If you are using end fed aerials or other un-balanced aerials then you are going to need a real earth as a counter balance.

I have been contemplating an outside aerial that would be multi-band endlessly but cannot make up my mind. I keep coming back to a co-ax supplied 9:1 balun outside with an earth from the balun down to an earth rod.

What is your set up?

73s G8NUP

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 08 June 2018 05:25 PM
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John Peckham

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I have an excellent paper on the subject on my hard disk written by Mr R. Page-Jones, G3JWI. Now where have I seen that name before?

If you PM me your email address I will send it to you.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 08 June 2018 05:55 PM
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MrPaul

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Hi there,and thanks for all of your replys.the antenna I am using is a inaverted l where you have two connections,one for the antenna and one for ground.the psu is connected to the mains earth.I pushed a Cooper pipe into the and just to see if the noise went away,and it did when I connected it to the back of the receiver.
It's all very complicated this earthing business.
Regards
 08 June 2018 05:56 PM
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John Peckham

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This thread motivated me to fire up the transceiver on 14MHz and using only 50W in to the dipole just got a 5&9 in to Slovenia. The other end thumping in to me but he was running 1500W in to a beam.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 08 June 2018 10:16 PM
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kellyselectric

Posts: 325
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Noise is a real problem on the HF bands these days I think unless you live right out in the sticks your going to get noise unfortunately the number of crappy switch mode wall warts is ever increasing and each one adds a bit more hash onto the bands. Most rigs run off external DC power supplys and I think commercially made supplys have the negative isolated from mains earth although ive seen diagrams for home brew supplys that clearly show the DC minus leg connected direct to mains earth so unless you've got one of them it should be fine here I have 3 supplys for my station 1 for the radio 1 for the powered speakers and autotuner and VLF converter and the big beast for the linear all are proper supplys with a mains tranny no switchmode rubbish here
 08 June 2018 11:10 PM
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mapj1

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I have an excellent paper on the subject on my hard disk written by Mr R. Page-Jones, G3JWI. Now where have I seen that name before?

Your current interlocuter may well have had a hand in reviewing that at draft stage, after all the OM and I are related you know, just 30 years apart...
Joking aside there is a later RSGB paper that supersedes his one,
here
but actually I think the newer one is a bit too 'PC' and almost tries to tell you that you either can't do anything or you must rewire your house, where really a bit of careful operating and thinking about the placement of equipment and what might be touched and so forth is enough in most cases. After all if you have enough energy to kill you on a coax connector with nothing but an understanding of what you are doing to stop you unscrewing it with the key down, then the rest of the safety case assuming you are an idiot rather pales. That and valved PAs with lethal HT.
These problems can sometimes lead one to contemplate rather odd configurations, that are well outside the BS7671 comfort zone, such as fuses in the feeders to the antenna and to its external earth, placed at the wall, to sever the link between indoors and out if a large diverted or fault current should flow.

-------------------------
regards Mike
 08 June 2018 11:30 PM
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chrispearson

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Just an observation ...

40+ years ago Brother was into ham radio and had an antenna at the top of a scaffolding pole which Father had allowed him to erect in the back garden. I have no idea about earthing arrangements. Nobody died.

But why ham radio nowadays? Isn't e-mail, Skype, or social media easier?
 09 June 2018 09:22 AM
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MrPaul

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Joined: 08 June 2018

Hi again to all,my 13.8v psu is connected to the mains earth.and my radio is connected to a two wire lead,- + so guys is it ok to put a ground wire from my radio the a ground rod near my back window.I have connected the wire up to test and the noise disappears.no more ac noise.is it ok to leave the ground wire connected to the radio?
Regards
 09 June 2018 09:46 AM
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sparkingchip

Posts: 10836
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Some years ago I was talking to the wife of a Herefordshire farmer with a fantastic radio setup, she drew a deep breath when I mentioned that her husband can contact people all over the world with Skype!
 09 June 2018 10:51 AM
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John Peckham

Posts: 8945
Joined: 23 April 2005

Mr Paul

Yes it is safe to connect your radio earth terminal to an electrode. Although I have a balanced aerial I might try connecting my transceiver earth terminal to earth to see if it will kill off some of my noise. The IET some time ago suggesting connecting an ancillary earth electrode to the incoming PME earth to hold down the touch voltage in the event of the loss of the supply neutral. Earthing the PME earth terminal to an electrode is one of the methods acceptable for the safety of vehicle charging points assuming that is you can get the resistance low enough!


Chris P.

The interest of amateur radio is the challenge of trying to communicate as far and as strongly as possible by your own efforts. The technical interest for me it is aerials. I spent a good few hours with an RAF photo reconnaissance analyst who asked me what I was interested in showed me books of photos of aerials that they used as reference source when studying air reconnaissance photos.

Of course for years we have had to live with all the standard jokes from Tony Hancock's radio amateur show which is available on Youtube, "friends all over the world but none round here"!

Sparkingchip

Radio amateurs do TV and data as well long before this internet malarkey!

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/

Edited: 09 June 2018 at 11:03 AM by John Peckham
 09 June 2018 11:00 AM
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mapj1

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But why ham radio nowadays? Isn't e-mail, Skype, or social media easier?

Very true, and I'd not like to rely on it as the only means of communication. But you mauy ask why some folk like horse riding, or rambling, now cars exist, or indeed why anyone in their right mind should enjoy ball games (golf/tennis/football). All of these are at face value futile diversions. Radio keeps the mind fit, and for those who enjoy things like field days and foxhunting, the body as well.
Also in other cases it can provide a social network for those who may not get out as much as they once could.
In my experience there is a soft divide between those who buy in ready-made kit and mostly enjoy the social aspects and the fun of not quite knowing who they will talk to, and those who enjoy fiddling with the station and building new antennas, preamplifiers and so forth for whom a contact is a name and number to see if the station is now working better than before. There are also a large number of folk now using machine generated modes to do funny things like communicate by meteor scatter where the channel is 'open' in very short bursts. Indeed the internet helps then by providing the ability to arrange or confirm that a contact has taken place.

But like climbing in the welsh mountains or going camping, it is ultimately done because you can and the appetite of various people to do more or less complex things varies a lot, and like the camping, there are lots of others for whom it would not really be the right thing. That's OK, they can take up another hobby...
>>>>>>>>>>>>>>>>>>>>>>>>>>

Now to return to the original question. This radio is on a DC supply that could have been a car battery, but in this case, is mains derived. Assuming the supply is in good order, I think the risk of bringing in an additional external earth, relative to the risks from bringing in the wires for the antenna you already have done is small.
However, when you are not using the radio, I suggest you unplug it from the mains, and avoid bringing mains earthed appliances into locations where you will might be able to hold both them and the radio at once. Try and use things like a desk lamp and if you have a logging laptop, that are either double insulated or also run from the same 12V as the rig. When going on hols or leaving it for a long time, disconnect and ground the antennas as well.
If you have children (or child like adults!) in the house, consider a strict 'no unsupervised fiddle fingers' policy, maybe even a lock on the door.
And, importantly, if at any time you observe any odd tingles from the earthed metal or antenna cables, or the mains supply seems to be misbehaving, stop and investigate.

-------------------------
regards Mike
 09 June 2018 11:05 AM
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MrPaul

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Joined: 08 June 2018

Hi there and thanks for the reply.at least I know its OK to use.many thanks mike
 09 June 2018 04:36 PM
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kellyselectric

Posts: 325
Joined: 22 July 2016

Can I just add this a contact by ham radio is an acheivment it means your efforts to build an areal or amplifier or whatever else have worked it a nice feeling when it all works like you want it to. I think talking to someone via tinternet is not really anything at all its the same as making a fonecall although I concede that sometimes getting a computer to behave does take an amount of luck or skill. A final thought on starting if you ha e a multimeter measure the resistance between the NEGATIVE terminal and the mains plugs earth pin should be virtually an open circuit if it is then your PSU is fully isolated and you can add a radio earth no problem at all
 09 June 2018 06:17 PM
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MrPaul

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Hi there,I have put a multi meter on there to test,set to resistance and I get the beep on the meter.
Regards
 10 June 2018 12:27 PM
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mapj1

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Its a bit tricky to comment on that statement - normally that means that whatever two bits of metal you were probing have a reasonably low resistance between them , but without knowing what items you were taking a measurement between I can't tell you if that was good or bad. (!)

-------------------------
regards Mike
 10 June 2018 01:00 PM
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MrPaul

Posts: 13
Joined: 08 June 2018

Hi there I put the multi meter probes in the negative and the earth and it had open circuit.I done what the guy said above.cheers
 10 June 2018 07:44 PM
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kellyselectric

Posts: 325
Joined: 22 July 2016

Glad you were able to check your PSU earthing but just a word was me that suggested it and im a GIRL!!
IET » Wiring and the regulations » Ham radio grounding,pme system

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